This invention relates in general to improved electrical components and, in particular, to different embodiments of logic circuit boards capable of interconnecting integrated circuit (IC's) devices and the like in an electrical circuit.
More specifically, but without restriction to the particular use which is shown and described, this invention relates to improved circuit or logic boards upon which IC packages, additional VLSI devices, and other components can effectively be interconnected in an electrical circuit. The circuit board of the invention provides a high density package capable of accommodating a greater number of different types of IC packages and the like as compared to the prior art. The invention herein disclosed also includes means for providing a dual voltage plane to better match the electrical requirements of the IC devices which are mounted on the board. The circuit board of the invention is further improved by an enhanced electrical grounding technique that protects and isolates connected IC circuits, particularly leadless, chip carrier sockets.
Printed circuit boards are commonly employed as an interface interconnecting IC devices and other components with the circuitry of a computer and the like. One type of circuit board commonly used in such applications mounts a plurality of typical IC devices which are connected to the circuit by a wrappable pin connection as is well-known. In many of such boards, a single voltage plane is provided on one side, while a ground plane exists on the opposite surface. The use of a single voltage plane, as is commonly provided in the prior art, renders the interconnection of a number of integrated circuit devices, many of which may have different electrical requirements, heretofore unsatisfactory.
In the past, the diverse electrical requirements of IC devices are often handled during the wire wrap process, by which the power to each pin is modified as needed. Wire wrapping permits dual voltage connections to be made through a "daisy-chain" which is detrimentally subject to breaks in pattern or poor reliability in use. Other boards having printed circuits require a physical modification of the etched, printed circuit to accommodate multiple voltages. Such physical alteration of the etched circuit is not readily accomplished nor are the results of these modifications wholly satisfactory. In general, prior designs are therefore incapable of readily and effectively meeting the varying electrical requirements of the components that must be accommodated by a circuit board.
Another problem associated with known circuit boards is the inability of these components to accommodate a range of pin spacings of different IC packages. In the prior art, terminals have been generally arranged in rows separated by an identical spacing, such as, for example, 0.300 inches apart. This known universal pattern, providing equal spacing between pin rows, limits the number and density of components having a number of different pin widths which can be accepted.
Based on design considerations, it is also highly desirable to employ a leadless, integrated circuit in the form of a chip mounted within a carrier as a component in computer circuits, since the device offers distinct, operative benefits. A leadless chip is faster and more sensitive than a conventional IC device. In the use of leadless chips, however, it is extremely important to protect its electrically dense circuitry from outside influences. Interference or noise imposed on a leadless chip carrier can result in a disruption of its capability for high performance. To insure its optimum level of operation, it is important that the chip be isolated as much as possible from the surrounding circuitry in order to attain effective operation. Known circuit boards have failed to provide means by which a leadless chip carrier is effectively shielded and grounded to optimize its performance and sensitivity within the circuit to which it is connected.